No Obesity Paradox-BMI Incapable of Adequately Capturing the Relation of Obesity with All-Cause Mortality: An Inception Diabetes Cohort Study

Association of body indices and risk of mortality in patients with type 2 diabetes

INTRODUCTION

A body shape index (ABSI) is independently associated with mortality in general population, but studies on the predictability of ABSI in the risk of mortality in patients with type 2 diabetes (T2D) are limited. We aimed to examine the independent and joint association of ABSI, body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), and body roundness index (BRI) with mortality in patients with T2D.

RESEARCH DESIGN AND METHODS

The study included 11 872 patients (46.5% women) aged 30 years and older and who took part in diabetes care management program of a medical center in Taiwan. Body indices were evaluated by anthropometric measurements at baseline between 2001 and 2016, and their death status was followed up through 2021. Multivariate Cox regression models were used to assess the effect of body indices on mortality.

RESULTS

During a mean follow-up of 10.2 years, 560 cardiovascular disease (CVD) deaths and 3043 deaths were recorded. For ABSI, WC, WHR, WHtR and BRI, all-cause mortality rates were statistically significantly greater in Q4 versus Q2. For BMI and WHtR, all-cause mortality rates were also statistically significantly greater in Q1 versus Q2. The combination of BMI and ABSI exhibited a superiority in identifying risks of all-cause mortality and CVD mortality (HRs: 1.45 and 1.37, both p<0.01).

CONCLUSIONS

Combined use of ABSI and BMI can contribute to the significant explanation of the variation in death risk in comparison with the independent use of BMI or other indices.

Impact of diabesity phenotype on cardiovascular diseases, major cardiovascular events and all-cause mortality

To investigate the longitudinal association of different phenotypes of diabetes and obesity with the incidence of cardiovascular disease (CVD), CVD- and all-cause mortality. A total of 5432 adults, aged ≥ 35 years and free of CVD were included in this cohort study. Diabesity phenotypes were defined in six categories based on the presence of diabetes (normal (NG), prediabetes and diabetes) and obesity (obese, non-obese). Fasting blood sugar, 2-h post prandial glucose, or using anti-diabetic medicines were used to define diabetes, and body mass index and waist circumference were used to define obesity. Cox proportional hazards models were used to estimate hazard ratios (HRs) for incident CVD, CVD- and all-cause mortality across these categories. After a median follow-up of 11.25 years, 819 CVD cases, 181 CVD deaths and 488 all-cause deaths occurred. In multivariable-adjusted models and irrespective of obesity definition, the phenotypes of normal glucose-obese, prediabetes-obese and pre-diabetes-non obese were not associated with CVD incidence in comparison with NG-non obese phenotype, however, the phenotypes of diabesity, either defined by general or abdominal obesity, were associated with increased risk of incident CVD events (HR = 1.42, 95% CI 1.01, 1.99, and HR = 1.46, 95% CI 1.07, 1.98, respectively). These findings were sex-specific and only in men with a phenotype of abdominal obesity-diabetes, a positive link was observed for CVD incidence (HR = 1.60, 95% CI 1.01, 2.52). No significant association was found between diabesity and death from CVD or all causes. Diabesity is a predictor of CVD and stroke incidence, but not CVD or all-cause mortality, among Iranians. This association is more pronounced amongst men than women.

The obesity paradox and diabetes

BACKGROUND

Obesity has been proven to be a risk factor for type 2 diabetes mellitus (T2DM) through numerous pathogenetic mechanisms. Unexpectedly, some studies suggest that subjects with overweight/obesity and T2DM have better clinical outcome than their normal weight peers. This finding is described as "obesity paradox" and calls into question the importance of weight loss in this specific population.

OBJECTIVE

This article is a narrative overview on the obesity and type 2 diabetes mellitus, particularly regarding the obesity paradox in T2DM patients.

METHODS

We used as sources MEDLINE/PubMed, CINAHL, EMBASE, and Cochrane Library, from inception to March 2020; we chose 30 relevant papers regarding the association of obesity with clinical outcome and mortality of patients affected by T2DM.

RESULTS

Many studies report that in patients with T2DM, overweight and obesity are associated with a better prognosis than underweight or normal weight, suggesting the presence of an obesity paradox. However, these studies have numerous limitations due to their mainly retrospective nature and to numerous confounding factors, such as associated pathologies, antidiabetic treatments, smoking habit, lack of data about distribution of body fat or weight history.

CONCLUSION

Literature data regarding the phenomenon of obesity paradox in T2DM patients are controversial due to the several limitations of the studies; therefore in the management of patients with overweight/obesity and T2DM is recommended referring to the established guidelines, which indicate diet and physical activity as the cornerstone of the treatment.

LEVEL OF EVIDENCE

Level V: narrative review.

The Evidence for an Obesity Paradox in Type 2 Diabetes Mellitus

Although overweight/obesity is a major risk factor for the development of type 2 diabetes mellitus, there is increasing evidence that overweight or obese patients with type 2 diabetes mellitus experience lower mortality compared with patients of normal weight. This paradoxical finding, known as the "obesity paradox," occurs in other chronic diseases, and in type 2 diabetes mellitus is particularly perplexing given that lifestyle intervention with one goal being weight reduction is an important feature of the management of this condition. We summarize in this review the findings from clinical and epidemiologic studies that have investigated the association between overweight and obesity (usually assessed using body mass index [BMI]) and mortality in type 2 diabetes mellitus and discuss potential causes of the obesity paradox. We conclude that most studies show evidence of an obesity paradox, but important conflicting findings still exist. We also evaluate if potential bias might explain the obesity paradox in diabetes, including, for example, the presence of confounding factors, measurement error due to use of BMI as an index of obesity, and reverse causation.

Impact of obesity on mortality in patients with diabetes: Meta-analysis of 20 studies including 250,016 patients

AIMS/INTRODUCTION

The impact of body mass index on mortality among patients with diabetes remains controversial. Therefore, we carried out a meta-analysis of pertinent studies.

MATERIALS AND METHODS

We searched OVID/MEDLINE, EMBASE and Cochrane databases for all reported studies, which investigated the relationship between body mass index and mortality in patients with diabetes. Summary estimates of hazard ratios (HRs) were obtained with a random effects model. Univariate meta-regressions were carried out.

RESULTS

A total of 20 studies including 250,016 patients with diabetes were identified. The results of the present study showed a significantly reduced risk of all-cause mortality in overweight patients (HR 0.82, 95% CI: 0.74-0.91, P < 0.0001, and I2 = 91.6%) as compared with normal weight patients. The survival benefits of obesity were only observed in the elderly patients (HR 0.69, 95% CI: 0.63-0.75, P < 0.0001, and I2 = 50.4%), but not in the younger patients (HR 1.01, 95% CI: 0.84-1.20, P = 0.96, I2 = 80.1%). Furthermore, the beneficial prognostic impacts on overweight (coefficient = 0.030, P = 0.041) and obesity (coefficient = 0.032, P = 0.010) were attenuated with clinical follow-up duration.

CONCLUSIONS

The present meta-analysis showed a significantly lower risk of all-cause mortality in overweight patients with diabetes compared with normal weight patients. However, the survival benefits of obesity were only observed among the elderly patients.

Nonlinear association of BMI with all-cause and cardiovascular mortality in type 2 diabetes mellitus: a systematic review and meta-analysis of 414,587 participants in prospective studies

AIMS/HYPOTHESIS

The relationship between BMI and mortality has been extensively investigated in the general population; however, it is less clear in people with type 2 diabetes. We aimed to assess the association of BMI with all-cause and cardiovascular mortality in individuals with type 2 diabetes mellitus.

METHODS

We searched electronic databases up to 1 March 2016 for prospective studies reporting associations for three or more BMI groups with all-cause and cardiovascular mortality in individuals with type 2 diabetes mellitus. Study-specific associations between BMI and the most-adjusted RR were estimated using restricted cubic splines and a generalised least squares method before pooling study estimates with a multivariate random-effects meta-analysis.

RESULTS

We included 21 studies including 24 cohorts, 414,587 participants, 61,889 all-cause and 4470 cardiovascular incident deaths; follow-up ranged from 2.7 to 15.9 years. There was a strong nonlinear relationship between BMI and all-cause mortality in both men and women, with the lowest estimated risk from 31-35 kg/m² and 28-31 kg/m² (p value for nonlinearity <0.001) respectively. The risk of mortality at higher BMI values increased significantly only in women, whilst lower values were associated with higher mortality in both sexes. Limited data for cardiovascular mortality were available, with a possible inverse linear association with BMI (higher risk for BMI <27 kg/m²).

CONCLUSIONS/INTERPRETATION

In type 2 diabetes, BMI is nonlinearly associated with all-cause mortality with lowest risk in the overweight group in both men and women. Further research is needed to clarify the relationship with cardiovascular mortality and assess causality and sex differences.

Body Mass Index-Related Mortality in Patients with Type 2 Diabetes and Heterogeneity in Obesity Paradox Studies: A Dose-Response Meta-Analysis

Objective

We conducted a systematic review and meta-analysis of studies to quantify the association between body mass index (BMI) and the risks of all-cause and cardiovascular mortality in patients with type 2 diabetes.

Methods

We included studies assessing the impact of BMI on all-cause and cardiovascular mortality in patients with type 2 diabetes. Data were combined using a random-effects dose-response model.

Results

Sixteen cohort studies on all-cause mortality (n = 445,125) and two studies on cardiovascular mortality (n = 92,841) were evaluated in the meta-analysis. A non-linear association was observed between BMI and all-cause mortality among patients with type 2 diabetes. With a BMI nadir of 28–30 kg/m², the risk of all-cause mortality displayed a U-shaped increase. With a BMI nadir of 29–31 kg/m², the risk of cardiovascular mortality exhibited a gradual non-linear increase for BMI > 31 kg/m². Subgroup analyses suggested that study location, diabetes duration, and smoking history may have contributed to heterogeneity among the studies.

Conclusions

An obesity paradox exists for patients with type 2 diabetes with respect to all-cause and cardiovascular mortality. Study location, diabetes duration, and smoking history might contribute to heterogeneity among obesity paradox studies of patients with type 2 diabetes.

Association of Weight Change after Colorectal Cancer Diagnosis and Outcomes in the Kaiser Permanente Northern California Population

BACKGROUND

Higher body mass index (BMI) is associated with incident colorectal cancer but not consistently with colorectal cancer survival. Whether weight gain or loss is associated with colorectal cancer survival is largely unknown.

METHODS

We identified 2,781 patients from Kaiser Permanente Northern California diagnosed with stages I-III colorectal cancer between 2006 and 2011 with weight and height measurements within 3 months of diagnosis and approximately 18 months after diagnosis. We evaluated associations between weight change and colorectal cancer-specific and overall mortality, adjusted for sociodemographics, disease severity, and treatment.

RESULTS

After completion of treatment and recovery from stage I-III colorectal cancer, loss of at least 10% of baseline weight was associated with significantly worse colorectal cancer-specific mortality (HR 3.20; 95% confidence interval [CI], 2.33-4.39; P_trend < 0.0001) and overall mortality (HR 3.27; 95% CI, 2.56-4.18; P_trend < 0.0001). For every 5% loss of baseline weight, there was a 41% increased risk of colorectal cancer-specific mortality (95% CI, 29%-56%). Weight gain was not significantly associated with colorectal cancer-specific mortality (P_trend = 0.54) or overall mortality (P_trend = 0.27). The associations were largely unchanged after restricting analyses to exclude patients who died within 6 months and 12 months of the second weight measurement. No significant interactions were demonstrated for weight loss or gain by gender, stage, primary tumor location, or baseline BMI.

CONCLUSIONS

Weight loss after diagnosis was associated with worse colorectal cancer-specific mortality and overall mortality. Reverse causation does not appear to explain our findings.

IMPACT

Understanding mechanistic underpinnings for the association of weight to worse mortality is important to improving patient outcomes. Cancer Epidemiol Biomarkers Prev; 26(1); 30-37. ©2016 AACR SEE ALL THE ARTICLES IN THIS CEBP FOCUS SECTION, "THE OBESITY PARADOX IN CANCER EVIDENCE AND NEW DIRECTIONS".

Determinants of mortality in patients with type 2 diabetes: a review

We aimed to review and summarize the evidence from accomplished trials analyzing factors influencing mortality in patients with T2DM and to provide some recommendations for targets and treatment in the European region. The following databases were searched for relevant trials: PubMed and the Cochrane Library. Of 3.806 citations, 134 trials met our inclusion criteria.

RESULTS

The reduction in lifetime for 65 + -years-old patients having less than 10 years T2DM amounts to 1.8 years. Having T2DM for more than 10 years lifetime will be reduced by 2.7 years. However, the lifetime shortening factor of T2DM will even be stronger for 40 + -years-old patients at onset. Males will lose 11.6 years of life and 18.6 QUALYs. T2DM among females will reduce life by 14 QUALYs by 22 years. From a statistical point of view, the highest mortality rate will occur in an over 55-years-old European smoking and non-compliant diabetic woman with alcohol abuse living in a rural area with a low level of education and a low socio-economic status. Furthermore, other co-morbidities such as cardiovascular diseases, gout, and depression affect mortality. Additionally, mortality will increase with a BMI over 35 and also with a BMI under 20-25. This refers to the obesity paradox indicating a higher mortality rate among normal weight patients with T2DM compared to overweight patients with T2DM. HbA1c-levels between 6.5 % and 7 % are associated with the lowest impact on mortality.

Body composition phenotypes and obesity paradox

PURPOSE OF REVIEW

The obesity paradox is a highly controversial concept that may be attributed to methodological limitations related to its identification. One of the primary concerns is the use of BMI to define obesity. This index does not differentiate lean versus adipose tissue compartments (i.e. body composition) confounding health consequences for morbidity and mortality, especially in clinical populations. This review will describe the past year's evidence on the obesity paradox phenomenon, primarily focusing on the role of abnormal body composition phenotypes in explaining the controversies observed in the literature.

RECENT FINDINGS

In spite of the substantial number of articles investigating the obesity paradox phenomenon, less than 10% used a direct measure of body composition and when included, it was not fully explored (only adipose tissue compartment evaluated). When lean tissue or muscle mass is taken into account, the general finding is that a high BMI has no protective effect in the presence of low muscle mass and that it is the latter that associates with poor prognosis.

SUMMARY

In view of the body composition variability of patients with identical BMI, it is unreasonable to rely solely on this index to identify obesity. The consequences of a potential insubstantial obesity paradox are mixed messages related to patient-related prognostication.

The Association Between Body Mass Index and All-Cause Mortality in Patients With Type 2 Diabetes Mellitus: A 5.5-Year Prospective Analysis

Abundances of study in different population have noted that obese cardiovascular disease (CVD) patients have a better prognosis than leaner patients, which refer to the phenomenon of obesity paradox. However, data on the association between body mass index (BMI) and mortality among Asian patients are limited, especially in patients with type 2 diabetes mellitus (T2DM). We investigate the association between BMI and all-cause mortality in Taiwanese patients with T2DM to define the optimal body weight for health.We conducted a longitudinal cohort study of 2161 T2DM patients with a mean follow-up period of 66.7 ± 7.5 months. Using Cox regression models, BMI was related to the risk of all-cause mortality after adjusting all confounding factors.A U-shaped association between BMI and all-cause mortality was observed among all participants. Those with BMIs <22.5 kg/m had a significantly elevated all-cause mortality as compared with those with BMIs 22.5 to 25.0 kg/m, (BMIs 17.5-20.0 kg/m: hazard ratio 1.989, P < 0.001; BMIs 20.0-22.5 kg/m: hazard ratio 1.286, P = 0.02), as did those with BMIs >30.0 kg/m (BMIs 30.0-32.5 kg/m: hazard ratio 1.670, P < 0.001; BMIs 32.5-35.0 kg/m: hazard ratio, 2.632, P < 0.001). This U-shaped association remained when we examined the data by sex, age, smoking, and kidney function.Our study found a U-shaped relationship between all-cause mortality and BMI in Asian patients with T2DM, irrespective of age, sex, smoking, and kidney function. BMI <30 kg/m should be regarded as a potentially important target in the weight management of T2DM.